Arrangement for subscriber line ring testing

ABSTRACT

An arrangement for automatically testing a plurality of subscriber lines, which are operationally connected to an electromechanical switching system is shown. Operational service is to be transferred from the electromechanical switching system to a digital switching system. This arrangement provides for automatically verifying whether the digital switching system is applying the proper ringing signal to each subscriber by a comparison with that applied by the electromechanical switching system.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to copending U.S. patent applicationSer. Nos. 445,803 and 445,802, having the same inventors and beingassigned to the same assignee.

BACKGROUND OF THE INVENTION

The present invention pertains to pre-cutover switching system testingand more particularly to an arrangement for an automated testing for theapplication of the proper ringing signals to the subscriber line.

When a new switching system, such as a GTD-5 EAX, is installed toreplace an existing switching system such as a step-by-step system,there is a testing interval during which time the subscriber's cablesare double jumpered to both switching systems. That is, each subscriberline will have an appearance on an inlet to each switching system. Thisdouble jumpering arrangement is made at the main distribution frame.

Typically, manual procedures were employed to verify a subscriber's lineconnection prior to cutover of the subscriber's service from oneswitching system to another. These manual procedures would be asfollows: first, an operator initiated a subscriber type access to theuntested switching system. Then, the operator sent out the callingnumber of the subscriber to be verified.

The untested switching system connected the operator to the subscriberand applied the ring signaling. If the subscriber answered the call, theoperator would ask whether their connection was audible and noise freeand verified that the correct subscriber had been reached. If thesubscriber didn't answer, the test must be retried.

These manual procedures are time consuming and uneconomical.Furthermore, the subscriber needs to become involved in the testingoperation.

Accordingly, it is the object of the present invention to provide aneconomical and automated arrangement for subscriber line verificationand ring testing which is devoid of subscriber participation orannoyance.

SUMMARY OF THE INVENTION

An arrangement for ring testing in a precutover switching configurationincludes a number of switching system subscribers which will ultimatelyhave their operative connection changed from a first switching system toanother switching system. At least two switching system subscribers areconnected to the first switching system. The first switching systemoperatively connects these subscribers to one another or to any otherswitching system subscribers.

The switching system subscribers of the first switching system aresimultaneously connected to a second switching system which is in anuntested condition. The second switching system includes a switchingnetwork connected to the subscribers, and a processor complex isconnected to the switching network.

A test switch train is arranged to access to the first subscriber andthis test train connection arrangement is operated to connect the firstsubscriber through the first switching system for a test access.

The regular switch train of the step-by-step exchange is also connectedto the first subscriber and is operated to connect any of the switchingsystem subscribers to any other first switching system subscriber.

In this arrangement for subscriber line ring testing the samesubscribers are also connected to a second switching system. The secondswitching system is in an untested condition and is not yet usable forinterconnecting said subscribers.

The second switching system has a switching network connected to each ofsaid plurality of subscribers for establishing a connection betweenthese subscribers.

The present arrangement for subscriber line verification and ringtesting further includes an automated arrangement for testing, that isconnected to the test train of the first switching system and is alsoconnected to the switching network of the second switching system. Thisautomated testing arrangement is operated to request the transmission ofa first ringing signal to the first subscriber through the switchingnetwork of the second exchange.

The automated arrangement for testing is connected to the firstsubscriber through the test train connection for this test access. Theswitching network is responsive to this request from the automatedtesting unit to generate and to transmit the first ringing signal to thefirst subscriber. The automated arrangement for testing is then operatedto detect this first ring signal via said test access through the firstswitching system and the testing arrangement is further operated tostore an indication of the characteristics of the detected first ringsignal.

The automated testing arrangement also connected to the regularconnection means for another connection to the first subscriber.

The automated arrangement for testing is then operated to transmit asequence of directory number signals to the regular connection path but,this sequence of directory number signals is one less than the number ofsignals required for connecting to the first subscriber.

The testing unit is then operated to transmit a third signal though thetest access to the test switch train connection.

The test switch train is operated in response to this third signal toallow connection of the regular switch train to the test connection.

The testing arrangement is then operated to transmit a second signal tothe regular connection.

The regular switch train connection is then further operated to transmita fourth signal having first and second characteristics to the testingarrangement via said test train connection.

The arrangement for testing is operated to detect the fourth signal andthe arrangement for testing is further operated to store an indicationof the first and second characteristics of the detected fourth signal.

DESCRIPTION OF THE DRAWING

The included drawing FIGURE is a schematic diagram of a pre-cutover, twoexchange environment for ring signal testing in accordance with theprinciples of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawing FIGURE, two telephone subscribers 1 and 2 areshown connected to a step-by-step switching system and to a digitalswitching system. Subscriber 1 is connected to these switching systemsvia the double jumper connection 5 and subscriber 2 is connected to bothswitching systems via the double jumper connection 6. A step-by-stepswitching system is shown, although this invention may be practiced withother electromechanical switching systems as well (e.g. No. 1 EAX, No. 2EAX, manufactured by GTE Automatic Electric Incorporated or others). Thedigital switching system is a time switching system such as, the GTD-5EAX (manufactured by GTE Automatic Electric Incorporated) or other timedivision switching systems having similar features of othermanufacturers.

Both subscribers 1 and 2 are connected to the digital switching systemvia relay arrangement 10. Relay arrangement 10 includes relay 11 havingmake-break contacts 12 and 13 which normally provide for simultaneouslyconnecting both subscribers 1 and 2 to switching network 30. Relay 11may be operated to transfer the connection of subscribers 1 and 2 toother circuitry instead of the switching network 30.

Subscriber 1 is connected through contacts 12 to line circuit 20. Linecircuit 20 includes test relay with make-break contacts 21 and batteryfeed device 22. Contacts 21 are normally closed to maintain subscriber 1connected to the switching network 30. Contacts 21 may be operated toenable the line of subscriber 1 to be connected to a test bus formaintenance accesses. Similarly, subscriber 2 may be connected to thistest bus via the operation of contacts 25.

The digital switching system includes a processor 40, which isoperatively connected to digital switching network 30. Line circuit 50and trunk circuit 51 are connected to the switching network 30 andprovide for connecting subscribers 1 and 2 to other subscribers or toother switching systems. Processor 40 includes a CPU arrangement with amemory containing a data base for operating the switching system. Thisdata base enables the digital switching system to associate particularsubscribers with particular line circuits and other equipment.

The digital switching system is in the precutover condition, that is notin a fully tested and operative configuration to provide telephoneservice to the subscribers. The step-by-step switching system is on-lineand provides active telephone service to subscribers 1 and 2, untilcutover of the digital switching system.

Subscribers 1 and 2 are thus connected via double jumpers 5 and 6respectively, to the connector bank 80. Quiescent operating potentialsare applied to each subscriber's line via a line relay 95 connected inseries with the break contact 96 of a cutoff relay. When a subscriber iscalled, the line relay 95 is disconnected by the operation of the cutoffrelay and the line is switched through to a battery feed device of aconnector or junctor or other similar circuit.

Line verification and ring testing (LVRT) system 60 is connected to boththe step-by-step switching system and to the digital switching system.LVRT 60 is a computer controlled test system which is arranged toprovide for a number of line verification and ringing tests of thedigital switching system before it is put into active service. Thesetests include: verifying that the subscriber line is free of shorts,grounds or foreign voltages; verifying that the assigned directorynumber will reach the same subscriber line from either the step-by-stepswitching system or the digital switching system; and verifying that theassigned director number will result in the same type of ringing(frequency and particular side of the line) to be applied by the digitalswitching system as does the step-by-step switching system. When thesefunctions have been successfully tested on each of the subscriber lines,the digital switching system may be placed into operational service andthe step-by-step switching system may be removed from service.

A line verification and ring testing system such as LVT-LRT system,model numbers 730 and 725, manufactured by Porta Systems of Syosset,N.Y., may be equipped to provide the functions as mentioned above.

LVRT system 60 tests the connection from subscriber 1 to the digitalswitching system. In the pre-operational configuration, the digitalswitching system has operated relay 11 to connect both subscribers 1 and2 to other circuitry which serves to open circuit subscribers 1 and 2from the switching network 30.

In order to test the line of subscriber 1 only, a unique path must beestablished through the digital switching system. The release of relay11 to its normally open condition will connect both subscribers 1 and 2to the switching network 30. Since only the line of subscriber 1 is tobe tested, processor 40 instructs the digital switching network 30 tooperate a test relay having contacts 25 to disconnect subscriber 2 fromthe switching network and connect the subscriber to the test bus, as if,the access is a test access. At the same time, processor 40 via digitalswitching network 30 operates relay 11 to its normally closed conditionfor connecting both subscribers 1 and 2 through contacts 12 and 13toward the switching network 30. Subscriber 1 is now connected throughbreak contact 12, line circuit 20 to the digital switching network 30.Subscriber 2 is connected via break contact 13 and make contact 25 tothe test bus. As a result, subscriber 1 has been isolated fromsubscriber 2 for testing purposes via the network 30 while at the sametime both subscribers 1 and 2 retain an operational access to thestep-by-step switching system.

LVRT system 60 initiates a test access to the required subscriberterminal of the step-by-step switching system via an incoming test trunkthrough distributor 90 and test connector 85. The LVRT system 60outpulses the directory number of subscriber 1, since this is the lineto be tested. The four terminating digits of the directory number areused for this purpose. Upon access to the subscriber 1 terminals of thetest connector cutoff relay is operated to operate break contact 96,thereby disconnecting line relay 95 from the connection. LVRT system 60is now connected to the line subscriber 1 via this metallic test accesspath. LVRT system 60 connects a self-contained test circuit to the lineof subscriber 1 through this metallic test access. This test circuitdetects foreign potentials, a ground connection or electrical shorts onthe line of subscriber 1. If these tests are unsuccessful, LVRT system60 initiates a printout on terminal device 99 indicating the failure.

Upon successful completion of the above mentioned tests, LVRT system 60connects to a line circuit 50 or a trunk circuit 51 of the digitalswitching system. LVRT system 60 sends out the seven digit or the fourdigit number of subscriber 1, for an access via a line circuit 50 or atrunk circuit 51, respectively. Special test programs are resident inthe memory of processor 40 of the digital switching system. The accessof line circuit 50 or trunk circuit 51 by LVRT system 60 will be treatedas a special call, that is a call associated with a pre-cutover linetest. Processor 40 instructs the digital switching network 30 to operaterelay 11 for its normally closed condition and to operate the test relayof make-break contacts 25 to connect subscriber 2 to the test bus and todisconnect subscriber 2 from battery feed device 26. Battery feed device22 is connected through contacts 21 and 12 to the line of subscriber 1.

LVRT system 60 connects its detector to the metallic access pathpreviously completed through distributor 90 and test connector 85. Thisdetector determines whether battery feed is applied to the line ofsubscriber 1 through the step-by-step switching system by the digitalswitching system.

The battery feed detector should detect 200 ohms to battery on the ringlead of subscriber 1 and 200 ohms to ground on the tip lead. If desired,LVRT system 60 may cause the digital switching system to apply aspecific tone for detection through the step-by-step switching system.An unsuccessful detection of battery feed results in a printout onterminal device 99 by LVRT system 60.

For a successful detection of battery feed, LVRT system 60 will transmita momentary on-hook signal through line circuit 50 or trunk circuit 51to the digital switching network 30. The test programs of processor 40interpret this signal as an instruction to apply ringing to the line ofsubscriber 1. The on-hook signal is applied for a duration ofapproximately 200 milliseconds. Switching network 30 will cause aringing signal to be applied to the line of subscriber 1 in accordancewith the data base characteristics stored in the memory of processor 40.This ringing will be transmitted through contacts 21 and 12 to the lineof subscriber 1. The ringing signal presence is verified by beingtransmitted via test connector 85 and distributor 90 to the LVRT system60.

LVRT system 60 connects a ringing sensor to the line of subscriber 1 viathe metallic access path through the step-by-step switching system. Theringing sensor determines the type of ringing signal that was applied bythe digital switching system. The processor of LVRT system 60 determineswhether the proper ringing frequency has been applied and whether it hasbeen applied to the appropriate side of the line (tip or ring lead). Theringing sensor employed by LVRT system 60 is of low impedance, so thatit will effectively shunt the telephone instrument of subscriber 1. As aresult, subscriber 1 will not detect any annoyance ringing. The detectedringing characteristics will be stored for later comparison.

Next, LVRT system 60 sends an on-hook (disconnect) signal to theswitching network 30 through to the line circuit 50 or the trunk circuit51. Switching network 30 will remove the applied ringing signal andoperate relay 11 to disconnect the digital switching system from theline of subscriber 1.

Then, LVRT system 60 outpulses the directory number of subscriber 1 intothe step-by-step switching system. Connection to the line of subscriber1 is established through a regular subscriber access via line circuit70, line finder 71, selector 72 and connector 80. Normally, connector 80would find the line of subscriber 1 busy and return busy tone to LVRTsystem 60, since prior connection has been established via the metallicaccess path through distributor 90 and test connector 85. To preventthis condition a bridge cutoff condition is established as describedbelow. The bridge cutoff capability is conventionally used to permitoperators at a local test desk to connect a line relay to a line undertest and thereby initiate a call for service or an "in-test." Suchequipment is well known in the telephone art. A typical system isdescribed in Automatic Electric Company Bulletin 815, titled "The Testand Verification Switch Train." Before LVRT system 60 dials the lastdigit of subscriber 1, the bridge cutoff is operated removing busy guardfrom the connector 80. Connector 80 will find the line of subscriber 1idle and extend ringing to the line.

Since a ringing sensor is connected to the line of subscriber 1 throughdistributor 90 and test connector 85, the ringing signal is returned toLVRT system 60. The ringing frequency and its application to aparticular side of the line will be detected and recorded as mentionedabove.

LVRT system 60 may cause the ringing information of both the digitalswitching system and the step-by-step switching system to simply beprinted on terminal device 99. LVRT system 60 may alternatively comparethe ringing characteristics of each switching system and print anydiscrepancy on terminal device 99. LVRT system 60 disconnects allaccesses to the step-by-step switching system and digital switchingsystems. Line verification and ring testing of the line of subscriber 1is completed and similar testing of each of the other subscriber lines,to be cut over into service on the digital switching system, mayproceed.

Although the preferred embodiment of the invention has been illustrated,and that form described in detail, it will be readily apparent to thoseskilled in the art that various modifications may be made thereinwithout departing from the spirit of the invention or from the scope ofthe appended claims.

What is claimed is:
 1. In a pre-cutover switching configuration, anarrangement for subscriber line verification and ring testingcomprising:a plurality of switching system subscribers; a firstswitching system connected to said plurality of switching systemsubscribers, said first switching system operated to connect any of saidswitching system subscribers to other switching system subscribers, saidfirst switching system comprising:said plurality of switching systemsubscribers including at least a first subscriber operatively connectedto said first switching system for said connection to other switchingsystem subscribers; and test connection means connected to said firstsubscriber and said test connection means operated to connect said firstsubscriber through said first switching system for a test access;regular connection means connected to said first subscriber and operatedto connect any of said switching system subscribers to said firstswitching system subscriber; said arrangement for subscriber lineverification and ring testing further comprising: a second switchingsystem connected to said plurality of switching system subscribers, saidsecond switching system being in an untested condition for connectingsaid subscribers, said second switching system comprising:said firstsubscriber connected to said second switching system; and a switchingnetwork connected to each of said plurality of subscribers forestablishing a connection between at least two of said subscribers; saidarrangement for subscriber line verification and ring testing furthercomprising: means for testing connected to said test connection means ofsaid first switching system and connected to said switching network ofsaid second switching system, said means for testing operated to requesttransmission of a first signal to said first subscriber via saidswitching network; said means for testing connected to said firstsubscriber via said test connection means for said test access; saidswitching network responsive to said request of said means for testingto generate and to transmit said first signal to said first subscriber;said means for testing operated to detect said first signal via saidtest access through said first switching system and said means fortesting further operated to store an indication of first and secondcharacteristics of said detected first signal; said means for testingconnected to said regular connection means for connecting to said firstsubscriber; said means for testing operated to transmit a sequence ofsecond signals to said regular connection means, said sequence of secondsignals including a number of second signals being one less than thenumber of signals for connecting to said first subscriber; said meansfor testing operated to transmit a third signal via said test access tosaid test connection means; said test connection means operated inresponse to said third signal to allow connection of said regularconnection means to said test connection; said means for testingoperated to transmit a second signal to said regular connection means;said regular connection means further operated to transmit a fourthsignal having first and second characteristics to said means for testingvia said test connection means; said means for testing operated todetect said fourth signal and said means for testing further operated tostore an indication of said first and second characteristics of saiddetected fourth signal.
 2. In a pre-cutover switching configuration asclaimed in claim 1 further including printout terminal means operatedupon storage of said detected first and fourth signal data to produce aprintout thereof.
 3. In a pre-cutover switching configuration as claimedin claim 1 further including a comparison means in said means fortesting operated after said operation to store an indication of saidfirst and second characteristic of said detected fourth signal tocompare said data with said stored indication of said first and secondcharacteristic of said earlier detected first signal, and thereafterfurther operated to store an indication of the results of saidcomparison.
 4. In a pre-cutover switching configuration as claimed inclaim 3 further including printout terminal means operated upon storageof said indication of said comparison to produce a printout thereof.